FIG. 9.

Fibrous wearable chemical sensor. (a) SEM image with low magnification of nanocellulose extracted from tunicate and CNT composite fiber. (b) Current–voltage curves obtained from fibers with a variety of CNT concentration. (c) Real-time NO₂ sensing for fibers with different concentrations of CNTs. (a)–(c) Reproduced with permission from Cho et al., ACS Nano 13, 9332 (2019). Copyright 2019 American Chemical Society.¹⁴⁶ (d) Cross section of nitrogen-doped reduced graphene oxide (nRGO) fibers. (e) Optical microscopy image of humidity sensing using nRGO fibers. (f) Humidity sensing using nRGO fibers mixed with platinum nanoparticles. (d)–(f) Reproduced with permission from Choi et al., Small 14, e1703934 (2018). Copyright 2018 John Wiley and Sons.¹⁴⁷ (g) Magnified SEM images of reduced graphene oxide fibers mixed with polypyrrole nanowires. (h) Repeatability of transistor-based sensing of glucose using fibers. (i) Source-drain current sensitivity of fibrous transistors to different concentrations of glucose. (g)–(i) Reproduced with permission from Wang et al., Biosens. Bioelectron. 95, 138 (2017). Copyright 2017 Elsevier.¹⁴⁸ (j) Optical image of fibers with embedded three electrodes. (k) Scalable production of thermally drawn fibers, capable of electrochemical sensing. (l) Recorded voltammograms of all-in-fiber electrochemical detection of paracetamol at different concentrations. (j)–(l) Reproduced with permission from Richard et al., ACS Appl. Mater. Interfaces 13, 43356 (2021). Copyright 2021 American Chemical Society.¹⁴⁹